Troubleshooting Lack Of Running Lights On Trailer When Other Light Functions Work

Question:

I have brake, turn signals and backup lights in my trailer just no running lights. The fuse is good on the truck and I nothing wrong with the plug. What else could I check?

asked by: ANTHONY A

Expert Reply:

Hi Anthony,

So you are getting 12 volts to the running light circuit at your 7-way? If not, then you have a break somewhere in the wire between the fuse and the 7-way. You can test your 7-way pins with a multimeter # PT89ZR to see how much voltage is running through. If you're getting less than 12 volts then that could also indicate an issue with the wiring as well. If the 7-way is getting 12 volts then the issue is with the trailer and you'll need to check the voltage at the junction box and then keep working your way back to the lights until you find the short.

It also wouldn't hurt to test the lights on a different trailer to rule out the vehicle being the issue. It could simply be that the lights have a burnt out bulb or just aren't functioning anymore.

expert reply by: Kevin C